恩施“6·24”暴雨中尺度系统特征分析

The characteristics of the mesoscale system in the "6·24" rainstorm of Enshi city

利用常规观测资料、自动区域站雨量、卫星TBB资料、雷达资料,对恩施州2016年6月24—25日发生的一次大范围暴雨过程进行分析。结果表明:本次强降水,具有典型的两槽一脊"单阻型"梅雨环流特征,在有利的大尺度环流背景下,在高空槽、低层低涡切变、西南急流、地面中尺度辐合线等中尺度天气系统的共同影响、相互作用下,形成了此次大范围强降水。此次暴雨空间上分布不均,局地性强,表现为明显的中尺度对流性特征,雷达回波图上降水性质表现为混合型降水,暴雨的直接影响系统是中β尺度对流系统,且中β尺度对流系统在多个中尺度对流云团合并后加强,时间尺度约为5 h。此次暴雨过程是在上干冷下暖湿强的大气层结不稳定条件下,梅雨锋、边界层辐合线和地形槽的触发作用将前期积累的能量释放产生的强对流天气,同时,副高外围西南气流将南海和西太平洋的水汽向恩施输送,为暴雨的发生提供了有利的条件。

The conventional observation data, automatic regional station rainfall, satellite TBB data and radar data were used to analyze the heavy rainstorm process occurred on June 24, 2016 in Enshi city. The results show that the rainstorm is the typical type which has two trough and a ridge and its name is ＂ single resistance type＂ meiyu circulation characteristics. The mutual influence and interaction of the favorable large scale circulation back- ground and the mesoscale weather system, such as the upper trough, low - level low vortex shear, southwest jet stream, surface mesoscale convergence line , and so on, formed the big range of strong precipitation. This rainstorm spatial distribution is uneven and its locality is strong, and its characteristic of mesoscale convection is obvious. The preeipitation is characterized by mixed precipitation from the radar echoes. The direct impact system of rainstorm is the mesoscale convection system, and the mesoscale beta convective system was strengthened after the merger of several mesoscale convective clouds, with a time scale of about 5 hour. This rainstorm is severe convection weather who occurred when the triggering action of meiyu front, boundary layer convergence line and terrain groove released the energy accumulated in the early stage in which it was dry and cold at the upper level, wet and warm at the lower troposphere. Meanwhile,The southwest airflow on the periphery of the periphery of the south China sea and the western Pacific Ocean sent to Enshi to provide favorable conditions for the occurrence of the rainstorm.